1. Field of the Invention
This invention relates to methods and apparatus for measuring air pollutants and is particularly directed to methods and apparatus for measuring sulphur dioxide.
2. Description of the Prior Art
In recent years, man has realized the fact that such essential natural resources as air and water are not unlimited in abundance and that survival requires that we take steps to prevent further pollution of these resources and, where possible, capture pollutants which have previously been released.
Among the major pollutants of air are oxides of nitrogen and sulphur. Numerous methods and apparatus have been proposed heretofore for measuring the various pollutants individually. However, none of the prior art devices have been capable of measuring oxides of both nitrogen and sulphur. Separate equipment has been required to accomplish this which, obviously, greatly increases the cost of pollution detection systems. Moreover, the most popular devices for measuring sulphur dioxide have required either bubbling the polluted air through an aqueous solution or reacting the sulphur dioxide with a hydrogen flame. Unfortunately, the bubbling method requires a liquid container, which is subject to spillage, while the hydrogen flame method requires a source of hydrogen, which becomes expensive and involves some inherent danger of explosion. Moreover, the flame is subject to being blown out or otherwise extinguished, which renders the device unreliable or useless. Other prior art detectors have made only gross measurements or have required frequent recalibration.